This invention relates to a turbine wheel of a hydrodynamic torque converter of the type having a lockup clutch and a turbine wheel.
A hydrodynamic torque converter comprising a lockup clutch and a turbine wheel of the initially mentioned type is the object of U.S. Pat. No. 5,441,135 originating from the applicant (which is not prior art). In the case of this torque converter, a bell-shaped housing shell, which rotatably receives an inward-flow turbine wheel, is connected with the outer shell of a pump wheel in a manner which is pressure-sealed and fixed with respect to movements, and with the turbine wheel by means of a lockup clutch which can be actuated by a clutch actuator of an axial-piston construction. The clutch disks of the lockup clutch are alternately non-rotatably held on two annular disk supports which are aligned concentrically with respect to the axis of rotation of the converter. In the case of this torque converter, a trouble-free heat dissipation is endeavored so that a sensitive, precisely apportionable control of the clutch slip of the lockup clutch is ensured which is actually used for saving fuel but, on the other hand, by regulating a defined slip condition, has the purpose of preventing the transmission of torque irregularities of the driving engine to the transmission line arranged behind the torque converter in the power flux. For this purpose, a housing-internal clutch space is provided in the case of the torque converter, which clutch space is bounded, in one direction of the axis of rotation of the converter, by a radial end wall of the housing shell and, in the opposite direction, is bounded by the turbine wheel. At a radially outer point, the clutch space has a flow connection with an annular gap between the pump wheel outlet and the turbine wheel inlet and, at a radially inner point, has a flow connection with a converter return flow pipe. The disk supports are provided with radial flow-through openings and are arranged to be situated with their whole length transversely in the inward flow of the clutch space which occurs between the two flow connections.
In the case of hydrodynamic torque converters, it is known to connect the lockup clutch by means of a torsional vibration damper with the hub of the turbine wheel (German Patent Document DE 39 15 186 C1; Japanese Patent Document JP-2 245562 A. in Patent Abstr. of Japan, Section M., Vol. 14 (1990), No. 572 (M-1061). In the case of one of these known constructions (Japanese Patent Document JP 4-224354 A. in Patent Abstr. of Japan, Sec. M, Vol. 16 (1992), No. 576 (M-1345"), a flange of the hub is in this case clamped in the directions of the axis of rotation between one flange respectively of the torsional vibration damper and the outer shell of the turbine wheel.
From KUKA Publication No. 19, of October 1975 (Reprint from DE-Z MM No. 70/1975), more generally, the prerequisites and possibilities of friction butt welding are known as well as the corresponding joining part preparation. Accordingly, the joining of parts with unequal cross-sections of the joint locations, like the welding of bolts or pipes on metal sheets, is to be carried out without difficulties. Plane or machined clamping surfaces of sufficient sizes would have to exist at the joining parts so that they can be clamped in precise positions and sufficiently tightly. Mentioned examples of applications are, among others, rotors for turbochargers as well as turbine wheels.
According to German Publication DE-Z Der Praktiker, No. 5, 1971--Page 5 (Reprint in KUKA Publication "Entwicklung und Anwendung von Reibschweissmaschinen in Deutschland" ("Development and Application of Friction Welding Machines in Germany"), it is indicated that manufacturing engineers and constructing engineers consider friction welding more and more. It is said that workpieces are reconstructed with respect to the process; the machining sequence, overmeasures of material and tolerances are changed; and additional prerequisites are therefore created for the further use of this fast and precise welding operation.
In VDI-Z, Volume 128 (1986) No. 20--October, Pages 801-812, reference is made to the fact that the telespectrum should comprise, among others, turbine wheels and rotor disk rims, and that friction welding was supposed to be successful for the manufacturing of high-precision components.
In German Publication DE-Z Schweissen und Schneiden, Year 20 (1968), Vol. 11, Pages 604-608, it is stated that friction welding as a joining process for butt seams has some very important advantages with respect to manufacturing as well as welding techniques in comparison to the joining technologies used here in the case of a number of motor vehicle parts.
It is an object of the present invention to design the turbine wheel with respect to its non-rotatable joints between the outer shell, the hub and the disk support in such a manner that an industrial-scale manufacturing is permitted which is simple with respect to manufacturing techniques and low in cost.
Based on a turbine wheel of the type mentioned above, this object is achieved according to the invention by providing an arrangement wherein the flange of the disk support is offset radially toward the inside with respect to the clutch disks,
wherein the hub has on its outer circumference a radial flange with a cylindrical outer jacket surface and with a face which faces the flange of the disk support and is situated in a flange plane which is normal with respect to the axis of rotation,
wherein the face of the flange of the hub facing the disk support has an axial projection which is concentric with respect to the axis of rotation, the outside diameter of the projection being smaller than the diameter of the outer jacket surface of the flange of the hub,
wherein the flange of the disk support is connected with the projection on the facing face of the flange of the hub and the flange of the outer shell is connected with the projection on the other face of the flange of the hub, each by means of friction welding, and
wherein on the flange of the hub in the transition area between the outer jacket and the face facing the flange of the disk support, parts-side form-fitting surfaces are developed for the rotational drive of the hub by means of counter-form-fitting surfaces of a receiving device of a friction welding machine which grips the hub and is rotationally driven.
According to the preferred embodiments of the invention, a hydrodynamic torque converter is thus constructed comprising:
a lockup clutch,
an outer shell holding turbine blades,
a hub non-rotatably joining the outer shell with a turbine wheel shaft,
and a disk support for non-rotatable joining clutch disks of the lockup clutch with the outer shell,
wherein said hub includes a radial flange which is connected on one axially facing side with the outer shell by a first friction weld connection and is connected at an opposite axial facing side with the disk support by a second friction weld connection, and
wherein the hub is provided with form-fitting surfaces at its side facing the disk support for accommodating rotational drive of the hub by means of counter-form-fitting surfaces of a receiving device of a friction welding machine which grips the hub and is rotationally driven.
In the case of the turbine wheel according to the invention, the non-rotatable joints between the hub, on the one hand, and the outer shell as well as the disk support, on the other hand, require only very limited space.
In the case of the turbine wheel according to the invention, the friction weld joint between the hub and the outer shell may be constructed with a larger diameter with respect to the axis of rotation of the converter than the friction weld joint between the hub and the disk support. As a result, both friction weld joints may be produced on one welding machine with a universal receiving device for the hub and the disk support.
In the case of the turbine wheel according to the invention, the joining parts do not require any special machining for the friction welding. The precision with respect to center deviations and wobbling, axial length, etc. are essentially determined by the friction welding machine and the receiving devices for the joining parts.
According to the invention, the machining time during the friction welding of the turbine wheel is very short.
In the case of the turbine wheel according to the invention, the joining operation can be automated and the process according to German Patent Application P 43 41 954.2 (corresponding to copending, commonly assigned U.S. application filed Dec. 9, 1994) can be used.
In the case of the turbine wheel according to the invention, after the welding operation with respect to the hub--outer shell joint is completed, the receiving devices for the outer shell which is now connected with the hub, can be moved back and, subsequently, the disk support can be clamped into the rotationally drivable universal receiving device which was used in the preceding welding operation for holding the hub.
In the case of the turbine wheel according to the invention, a reinforcing plate is eliminated which would have to be soldered to the flange of the outer shell if the flange of the hub and the flange of the outer shell and the flange of the disk support were non-rotatably fixed with respect to one another by a common riveted connection.
At the end of the friction welding operation after the cooling or during the cooling of the welding zone, because of the still rotating rotationally drivable receiving device, its coaxiality with respect to the other receiving device may be cancelled. This coaxiality error will be the larger the more elastic the machine frame between the receiving devices. These elasticities may be eliminated by the use of a bearing arrangement for the mutual centering of the receiving devices in the center of the axis of rotation.
For avoiding coaxiality errors, which are caused by the temperature course of the welding machine, in addition to the mutual centering of the receiving devices, the arrangement may be made in such a manner that the receiving device for the outer shell has a special part which, with respect to the receiving device, is fixed with respect to movements but, in the directions which are perpendicular with respect to the axis of rotation, is arranged with a limited elasticity and is used for the actual holding of the outer shell.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.